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Leaning towards my alt has given up....11.2V across terminals at idle....so I started shopping rebuilt units. What is the list consensus on these suppliers:

Bimmerworld - rebuilt Bosch; 2year warranty; $390; $60core; total = $450
ECS tuning - rebuilt Bosch; 1year warranty; $312; $70core; total = $481
FCP Euro - rebuilt Bosch; lifetime warranty; $308; $100core; total = $408
Rock Auto - rebuilt Bosch; 2year warranty; $254; $66core; total = $320

I would like to add that the pics on these sites all seem identical parts with bosch SKU AL0804X. Bimmerworld and ECS aren't competitive....FCP I haven't done business with yet but I like the idea of lifetime warranty....Rock Auto has a really easy core return process with discount return shipping labels which I can attest to. Not sure if the lifetime warranty is worth 88 bucks with possible complexity of core return if I go with FCP.

Any other folks I should consider
 

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I've dealt with ECS, FCP and RA. All have great customer service. RA is my favorite as far as pricing, but for some things it makes sense to use FCP given their lifetime warranty. How much that warranty is worth is up to you.
 

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Alternators, especially rebuilds, are a complete crapshoot anymore. I recommend you support your local parts supplier (NAPA, AutoZone etc.) and buy a NEW alternator. Don't go with a rebuild. If you do then go with Bosch. They seem to be the most reliable rebuild. I went through several rebuilds before buying a new AutoZone product. My local AutoZone bends over backwards for me when I ask them for help.

Just another alternator alternative for you.
 

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What a coincidence as I am about to embark upon this job again for the third time. Lifetime Bosch FCP unit on its way, the first one from them lasted only since October 2018 :(

Genuine part at FCP is like $800! Genuine voltage regulator is like $500+ alone!!


Maybe in this particular instance there is something different/better in the Genuine part?


Sent from my iPhone using Tapatalk
 

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Alternators, especially rebuilds, are a complete crapshoot anymore. I recommend you support your local parts supplier (NAPA, AutoZone etc.) and buy a NEW alternator. Don't go with a rebuild. If you do then go with Bosch. They seem to be the most reliable rebuild. I went through several rebuilds before buying a new AutoZone product. My local AutoZone bends over backwards for me when I ask them for help.

Just another alternator alternative for you.
Sure about that? Because none of those stores sold alternators new except for Napa. And the lone new one they wanted $1300!! I'd stick with a rebuilt Bosch from FCP because of the lifetime warranty.

Sent from Uranus with Love.
 

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It really depends on your plans with the car. Plan on keeping it “forever”, then I’d lean more heavily towards FCP. From RockAuto it will come with a 2 year warranty, so you’re still protected against short term failure. There’s a lot of variables with these decisions, but if you don’t think you’ll keep the M5 for more than a few years, it doesn’t make sense to pay the FCP premium for a part like this.
 

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Sure about that? Because none of those stores sold alternators new except for Napa. And the lone new one they wanted $1300!! I'd stick with a rebuilt Bosch from FCP because of the lifetime warranty.

Sent from Uranus with Love.
Yes I am, but should clarify. My e39 is a 530i and not an M5 so that likely affects availability etc. I have heard good things about the Bosch rebuilt alternators. My recommendation is to stay away from any other rebuilds.

I'm also fortunate in that my local AutoZone is a regional delivery hub. That store typically has more items in stock.
 

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What a coincidence as I am about to embark upon this job again for the third time. Lifetime Bosch FCP unit on its way, the first one from them lasted only since October 2018 :(

Genuine part at FCP is like $800! Genuine voltage regulator is like $500+ alone!!


Maybe in this particular instance there is something different/better in the Genuine part?


Sent from my iPhone using Tapatalk
So supposedly the M5 alternator fits the non-M I6, so perhaps the other way around would also work.
 

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Nope. Physically it looks very similar to the I6 alternators.
Sorry I can't remember the details, but I do remember the high points. Now I will have to go back and search for my own or 68fb posts to find those details. Sucks getting old.
The Basic issue is the output many more amps come from the M5 alternator. The next issue is the semi smart system and the voltage regulator. The DME controls the alt. it turns it off and on frequently. You can see this in a normal drive when you take your foot off the gas under a certain rpm the alt is turned off and then it stays off until a stable idle is reached but then only gives part power. It is not that a smart voltage reg is needed but a durable one appears to be needed.
Just go back a few years and read the stories of the guys that decided an after market VR would do the job.
 

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Hmmm, so perhaps it's the constant turning on and off of the alternator that eventually kills the voltage regulator? I can confirm the M5 alternator is NOT water cooled like the 540i.
 

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Discussion Starter #14
Update, I've decided to try FCP Euro...local Indy's aren't doing good business and FCP sent me a 5% coupon as an reminder/incentive to complete the transaction already in my shopping cart. Free shipping too.

Thanks everyone, here's to an easy install. Might put on my supersprint headers I've had sitting here at the same time, fix washer fluid reservoir leak, etc insert whatever else creaps up while I'm in there :)
 

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Hmmm, so perhaps it's the constant turning on and off of the alternator that eventually kills the voltage regulator? I can confirm the M5 alternator is NOT water cooled like the 540i.
That is what has been suggested, it was further surmised that the whole system takes abuse, diodes even armature. Likely why a different smart system was used in the later cars. I tried a after market, near no name reg and it lasted until the armature failed, then I just bought a near new one out of a wreck. 40K on it considering my factory one lasted to 250k km it was new enough.
 

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Sorry I can't remember the details, but I do remember the high points. Now I will have to go back and search for my own or 68fb posts to find those details. Sucks getting old.
The Basic issue is the output many more amps come from the M5 alternator. The next issue is the semi smart system and the voltage regulator. The DME controls the alt. it turns it off and on frequently. You can see this in a normal drive when you take your foot off the gas under a certain rpm the alt is turned off and then it stays off until a stable idle is reached but then only gives part power. It is not that a smart voltage reg is needed but a durable one appears to be needed.
Just go back a few years and read the stories of the guys that decided an after market VR would do the job.
M5 alternator is only 120A, M54 alternators go up to 155A. The voltage regulator might be semi-smart, but the DME doesn't do any communication with it, it certainly doesn't turn it on and off on the E39 M5. The connection from the alternator to the DME is an output that the DME doesn't evaluate (you can disassemble the software and check yourself, the alternator ADCount is on address 0xFFF2BE of the slave processor). That signal is simply relayed to the instrument cluster which then will turn on the battery light if the voltage from the alternator is less than 1/2 of the battery voltage (and in the case of the semi-smart voltage regulators, they'll set that pin to ground based on a few other conditions to signal the battery light to come on with more than just voltage criteria). Some alternators had a smart start system (unclear if the M5 did) where the alternator would set the current limit to 0A during engine start to make starting a little easier. Per BMW, there's no difference otherwise. https://www.newtis.info/tisv2/a/en/e39-m5-lim/wiring-functional-info/power-train/engine/alternator/alternator/XfOfPjy

Newer BMWs do have a serial interface between the alternator and DME, and at some point BMW introduced the so-called efficient dynamics which does turn the alternator off while on throttle and turns it on while off throttle (the idea was to have a minor regenerative braking effect).

BMW's training documentation for the E39 M5 does not mention an intelligent alternator of any sort.

If your voltage was going low off throttle, I suspect that was a soft-failed alternator. The E39 instrument cluster would turn the battery light on if the alternator was truly turning off.
 

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Good call on FCP. I've noticed their pricing has become more competitive in addition to the warranty (and occasional 5% code). win-won nowdays!
 

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M5 alternator is only 120A, M54 alternators go up to 155A. The voltage regulator might be semi-smart, but the DME doesn't do any communication with it, it certainly doesn't turn it on and off on the E39 M5. The connection from the alternator to the DME is an output that the DME doesn't evaluate (you can disassemble the software and check yourself, the alternator ADCount is on address 0xFFF2BE of the slave processor). That signal is simply relayed to the instrument cluster which then will turn on the battery light if the voltage from the alternator is less than 1/2 of the battery voltage (and in the case of the semi-smart voltage regulators, they'll set that pin to ground based on a few other conditions to signal the battery light to come on with more than just voltage criteria). Some alternators had a smart start system (unclear if the M5 did) where the alternator would set the current limit to 0A during engine start to make starting a little easier. Per BMW, there's no difference otherwise. https://www.newtis.info/tisv2/a/en/e39-m5-lim/wiring-functional-info/power-train/engine/alternator/alternator/XfOfPjy

Newer BMWs do have a serial interface between the alternator and DME, and at some point BMW introduced the so-called efficient dynamics which does turn the alternator off while on throttle and turns it on while off throttle (the idea was to have a minor regenerative braking effect).

BMW's training documentation for the E39 M5 does not mention an intelligent alternator of any sort.

If your voltage was going low off throttle, I suspect that was a soft-failed alternator. The E39 instrument cluster would turn the battery light on if the alternator was truly turning off.
That is likely a description pre 2000 we have found old info left in TIS frequently. If the DME did not turn it off then we would not see the alt turned off when you take your foot off the pedal once the rpm drops below a certain rpm ~1600 -1800. Go get in your car and take it for a drive and see for yourself. Everyone's car behaves that way. I mean we have only been discussing this for 10 years. It does other dumb things too because it is not a "smart system".
Then bring up the WDS and look for the updated description of how the alt works.
Then I will dig out the info to discuss this further.
 

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That is likely a description pre 2000 we have found old info left in TIS frequently. If the DME did not turn it off then we would not see the alt turned off when you take your foot off the pedal once the rpm drops below a certain rpm ~1600 -1800. Go get in your car and take it for a drive and see for yourself. Everyone's car behaves that way. I mean we have only been discussing this for 10 years. It does other dumb things too because it is not a "smart system".
Then bring up the WDS and look for the updated description of how the alt works.
Then I will dig out the info to discuss this further.
I've extensively disassembled the DME and rewrote some of the alternator code on the CSL version of the MSS54HP. And before you say it, in this case the code is equivalent between the MSS52/MSS54/MSS54HP. The DME has no capability of turning off the alternator. MAYBE the voltage regulator itself signals the alternator to turn off and outputs a high enough voltage on the D+ pin to keep the light off, but that won't be by a DME command. There is no BMW documentation of such a function that I can find. In which case replacing the alternator with a dumb alternator would work fine - the DME wouldn't give a crap.

You guys might have been discussing this for a decade, but this wouldn't be the first time that a forum's dogma was straight up wrong.

Edit: In fact, the voltage regulator (12311713491) is shared with the M43 (i.e e36 era), M52TU, and M62... so unless you think all of those cars had smart alternators with DME signaling (they don't), that's something this forum just has wrong..

Found your old posts where you copied/pasted to the same blurb I linked to: Can the e39 m5 run with no battery connected?

Your explanation there is also wrong. The DME doesn't communicate with the alternator over that wire. That wire simply feeds the voltage regulator/controller output to the DME. That will normally be equal to system voltage. That feeds into an analog to digital converter to digitize the signal which is then fed to the slave CPU (and you can read that digital value on 0xFFF2BE). Internally, that pin is connected to the output on X60004 Pin 1 (check with your multimeter, they're electrically continuous).

On the MSS52, MSS54, and MSS54HP CSL - it ends there, the DME does not use the voltage regulator output for anything other than letting you read the alternator voltage via a DS2 command. On the MSS54HP non-CSL, BMW added a small bit of code that evaluates the alternator voltage and triggers the instrument cluster's battery light over the CAN-bus. Whether it's the instrument cluster or the DME in the case of the MSS54HP, that battery light is triggered when the output voltage falls below 1/2 of the system/battery voltage. The "smart" voltage regulator will ground the pin (i.e set it to 0v) under certain circumstances, such as overvoltage and charge cable disconnect. This too would obviously trigger the light since 0 will be less than 1/2 of the system voltage.

That's it. The wire going to the DME is not a data connection of any sort, let alone a bidirectional one.
 

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Wrong, you did not find any of the test posts or you ignored them. I had a led test light hooked up to that feed for two years I know when it turns off. The switch is clearly turned off when the RPM falls.
And frankly unless you did this test on a 52 you are assuming things. Explain why all the cars do the same thing?
No one said it is a data connection just that the DME throws the switch and turns the darn thing off until a stable idle is reached. Exactly what the WDS says it does. Maybe you are confused by the term smart, it is sarcastic because the system is dumb as heck. We do know it is dumb and that was why we called it smart.
And frankly this would not be the first time a software guy assumed things and got it way wrong.
Just answer the question on how all M5s built after 11/99, maybe it was 09/99, have this same behavior? I have no clue if the 54 behaves the same.
The system also has something else that ends up killing batteries as they age, but we can do that next.
So I take it you don't have a M5, that would explain you remark on the higher output alt. The only other alt that will squeeze into the tiny hole is one from a E34 I6. It is only 100 amps. Go back and search in the era when the kids started buying these cars and thought that 540 parts would work.
 
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